Dr Edmond Ma invents metal complex to rapidly detect lead contamination in water

(Front) Mr Lin Sheng, (back, from left) Dr Edmond Ma and Miss Ko Chung-nga invent a luminescent complex that can rapidly and sensitively detect lead ions in water using only a portable device.

A schematic diagram of the luminescent switch-on assay that monitors the presence of lead ions using a G-quadruplex-selective probe.

Dr Edmond Ma, Associate Professor of our department, and his collaborators have invented a luminescent metal complex which rapidly detects lead ions in water. This new DNA-based method requires less than 10 minutes to sensitively detect lead contamination using only a portable instrument and a laptop. This cost-effective method attains results with greater accuracy and sensitivity. The team has filed a provisional patent for this invention in the US.

The project entitled “A luminescent iridium(III) complex and its uses thereof for the G-quadruplex-based switch-on rapid detection of lead ions” is the result of a collaboration between Dr Edmond Ma, Dr Duncan Leung Chung-Hang, Associate Professor, Institute of Chinese Medical Sciences of the University of Macau, HKBU PhD student Mr Lin Sheng and Miss Ko Chung-nga (Chemistry, Year 4).

The team developed the synthesis and use of a luminescent iridium(III) complex for the construction of a label-free G-quadruplex-based assay for the rapid detection of lead ions in aqueous solution. Dr Ma said, “The presence of lead ions is known to induce a structural change in DNA from single-stranded to a special conformation called a G-quadruplex. This change in structure is recognised by the luminescent iridium(III) complex with an enhanced emission response, allowing the system to function as a luminescent “switch-on” probe for lead ions. Therefore, we could use this assay to determine whether the water sample contains excessive lead ions.”

Their experiments showed that as the concentration of lead ions increased, the system experienced a gradual increase in luminescence intensity. This indicates that this G-quadruplex-based sensing platform is a potential method to rapidly detect lead ions in tap water, offering a promising tool for environmental and water safety monitoring.

Dr Ma also explained that conventional methods for detection of lead in water tend to take a longer time (more than 15 minutes), require steps involving expensive pre-labeling (with an intermediate agent such as fluorophore), and may produce false positive results owing to influence by other compounds in real water samples. In contrast, the method developed by their team shows good selectivity towards lead ions and has the ability to detect lead ions in drinking water at concentrations as low as 10 ppb (the World Health Organization safety standard). Due to the versatility of DNA and the iridium(III) complex, the team’s next step is to develop paper testing strip based on the same mechanism, which could allow the general public to conveniently test the presence of lead ions in drinking water at home, with ease of use comparable to that of a pH test paper or pregnancy test kit.